1. Field of the Invention
The present invention relates to a radio communication apparatus and a send and receive control system for using the same, and more particularly relates to a send and receive control system to be used in a circuit in which a power amplifier is bypassed or a circuit in which the power source of the power amplifier is controlled to be ON or OFF.
2. Background Art
Generally, in a transmitter installed in a mobile machine, the transmission output power of the transmitter is controlled by the control signal from the base station. In this type of transmitting output power control system, when carrying out the control of the transmission output power with a wide dynamic range with linearity, a reduction of a current consumption efficiency at the time of low output transmission requires a reduction of the current consumption.
One of the measures for reducing the current consumption in the transmission output control is realized by a variable control of the gate bias by use of a gate bias variable circuit so as to obtain an optimum DC characteristic (idle current) for the transmission output.
However, since it is not possible to squeeze the DC characteristic infinitely to preserve the linearity of the power amplifier, there is naturally a limit in the reduction of the current consumption at the low output transmission, and it becomes impossible to further reduce the current consumption when the output level is below the prescribed low level.
A first method for solving the above described problem has been proposed by the present inventor by bypassing the power amplifier, since amplification of the signal is not necessary when the transmission output is low.
In a phase deviation modulation system such as the CDMA (Code Division Multiple Access) radio communication system, which is used in the digital radio communication systems, data is transmitted by allocating the data in each phase of the carrier wave. For example, in a QPSK (Quadriphase Phase Shift Keying) system, each data is transmitted by allocating to it as a symbol on the I-Q plane, such that the data xe2x80x9c00xe2x80x9d is allocated the phase xcfx80/4, the data xe2x80x9c10xe2x80x9d is allocated the phase 3 xcfx80/4, the data xe2x80x9c11xe2x80x9d is allocated the phase 5 xcfx80/4, and the data xe2x80x9c01xe2x80x9d is allocated the phase 7 xcfx80/4.
In this case, the phase of each datum is shifted by xcfx80/4, and it is possible rotate the entire phase, that is, the standard phase by the angle of xcfx86, maintaining each phase difference at xcfx80/4. For example, in interpolated synchronous detection used in the phase deviation modulation system, the standard phase is rotated for each slot provided in the main signal, and the standard phase for each data in the slot is rotated.
However, in the radio communication apparatus with the above-described system, since the amounts of phase variation of a variable gain amplifier varies with the gain when the variable gain amplifier is provided in a modulating portion or in a demodulating portion of an analog circuit portion, and since the relative phase relationship between the input signal and the output signal of the variable gain amplifier is deformed when the gain change is generated, an error in detecting the standard phase based on the pilot signal arises due to the phase change based on the gain variation, which causes a problem of generating a detection error for each switching unit of the gain in the slot.
In order to solve the above described problem, the present inventor has proposed a second method, in which the phase rotation at the amplifier is compensated by the base band signal.
In the above-described conventional radio communication apparatus, in the first method for reducing the current consumption by bypassing the amplifier when the transmission power is small, it is not possible to compensate the phase rotation caused by bypassing the amplifier.
The present inventor has also proposed the second method for reducing the current consumption by compensating the phase rotation at the amplifier by the base band signal.
In the above-described conventional radio communication apparatus, the first method for reducing the current consumption by bypassing the power amplifier when the transmitting power is small is not capable of compensating the phase rotation, because the second method does not include a device to compensate the phase rotation.
The second method which compensates the phase rotation at the amplifier by the base band signal cannot respond to an instantaneous phase change such as the bypass switching.
The present invention was made to solve the above described problems. It is, therefore, an objective of the present invention to provide a radio communication apparatus capable of bypassing the power amplifier, and comprising a phase compensating circuit disposed in the bypass route for bypassing the power amplifier for compensating the sudden rotation of the phase due to switching the route.
According to the present invention, a radio communication apparatus provided with a power amplifier which can be bypassed comprises: a normal route passing through the power amplifier and a bypass route for bypassing the power amplifier; and a phase compensation circuit disposed in said bypass route for compensating the sudden phase rotation when switching said two routes.
According to the present invention, in the radio communication apparatus, provided with a receiving amplifier whose power source can be universally controlled to be ON or OFF, and which is disposed on a receiving route, the radio communication apparatus comprises a phase compensation circuit, disposed after said receiving amplifier on said receiving route, for compensating for the sudden phase rotation due to the on/off switching of said power source.
According to the present invention, in a send and receive control system, provided with a power amplifier which can be bypassed, the phase compensation circuit for compensating for the sudden phase rotation due to the route switch is disposed in a bypass route for bypassing said power amplifier.
Furthermore, in the send and receive control system, the amount of the phase rotation of said phase compensation circuit can be controlled by a voltage, and the send and receive control system can comprise a memory device for storing a phase adjustment value for said phase compensation device.
That is, in the send and receive control system according to the present invention comprising a circuit which can bypass the amplifier or which can execute the on/off control of the amplifier, although the phase of the output signal is suddenly rotated, this phase rotation of the output signal of this system can be prevented by comprising a phase compensation circuit and by providing in advance the amount of phase change as data in a memory device.
Thereby, compensation of the phase rotation by the phase compensation circuit arising in a circuit which can bypass the amplifier allows preventing the phase rotation and allows stable radio communication.